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let ubus, sub, listener, global;
const dhcp_parser_proto = {
reset: function() {
this.offset = 0;
},
parseAt: function(offset) {
let id = hex(substr(this.buffer, offset, 2));
let len = hex(substr(this.buffer, offset + 2, 2)) * 2;
if (type(id) != "int" || type(len) != "int")
return null;
let data = substr(this.buffer, offset + 4, len);
if (length(data) != len)
return null;
return [ id, data, len + 4 ];
},
next: function() {
let data = this.parseAt(this.offset);
if (!data)
return null;
this.offset += data[2];
return data;
},
foreach: function(cb) {
let offset = 0;
let data;
while ((data = this.parseAt(offset)) != null) {
offset += data[2];
let ret = cb(data);
if (type(ret) == "boolean" && !ret)
break;
}
},
};
function dhcp_opt_parser(data) {
let parser = {
offset: 0,
buffer: data,
};
proto(parser, dhcp_parser_proto);
return parser;
}
function parse_array(data)
{
return map(match(data, /../g), (val) => val[0]);
}
function parse_string(data)
{
return join("", map(parse_array(data[1]), (val) => chr(hex(val))));
}
function parse_macaddr(addr)
{
return join(":", parse_array(addr));
}
function dhcp_cb(msg) {
if (msg.type != "discover" && msg.type != "request")
return;
let packet = msg.data.packet;
if (!packet)
return;
let opts = substr(packet, 240 * 2);
if (length(opts) < 16)
return;
let macaddr = parse_macaddr(substr(packet, 28 * 2, 12));
opts = dhcp_opt_parser(opts);
opts.foreach((data) => {
let id = data[0];
switch (id) {
case 12:
typestr = "%device_name|dhcp_device_name";
data = parse_string(data);
break;
case 55:
typestr = "dhcp_req";
data = join(",", map(parse_array(data[1]), (val) => hex(val)));
break;
case 60:
typestr = "dhcp_vendorid";
data = parse_string(data);
break;
default:
return;
}
global.device_add_data(macaddr, `${typestr}|${data}`);
});
}
function init(gl) {
global = gl;
ubus = gl.ubus;
gl.weight.dhcp_req = 1.1;
gl.weight.dhcp_device_name = 5.0;
sub = ubus.subscriber(dhcp_cb);
listener = ubus.listener("ubus.object.add", (event, msg) => {
if (msg.path == "dhcpsnoop")
sub.subscribe(msg.path);
});
sub.subscribe("dhcpsnoop");
}
return { init };
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